My two cents, having experience in dealing with a hoarder and the physical effect of his hoarding on his house:
Q1, you say you ran out of shelf space and started piling books on the floor.
Something like this is okay.
Something like this or worse, and in several rooms, is not okay.
Depending on factors like how many books you have piled up and in how many rooms, the condition and age of your house, and any other fundamental structure problems, your house could potentially be hazardous. I imagine thousands of books stacked everywhere would put a rather heavy stress on the support beams.
County officials are obligated to make sure it is safe for you to be in your own home. Now, whether they are accurate in their assessment, or just making a mountain out of a molehill, we can't be sure, because we only know your side of the story.
Just putting this out there: how do you keep the house clean with all the books in the way? Maybe there is more cause for alarm than just "piles of books".
You say you're already boxing everything up, right? Then you should be happy to allow them in for a visit, so you can prove that you're already alleviating the situation yourself. No need to be so defensive or paranoid, unless there is a bigger problem you are trying to hide...? In which case, it would be wise to accept the help now, before the amount gets so out of control that you lose all of your possessions and possibly even the house itself.